What can I do to prepare for my baby's arrival in the first trimester?

ENjoy. Enjoy the ride and consider taking a first time parent's course and finding a good OB and pediatrician.
Pamphlets attached. This is quite an open-ended question so i decided to post some acog pamphlets that may be of interest: a father's guide to pregnancy- http://www.Acog.Org/publications/patient_education/bp032.Cfm & travel during pregnancy- http://www.Acog.Org/publications/patient_education/bp055.Cfm & getting in shape after your baby is born- http://www.Acog.Org/publications/patient_education/bp131.Cfm.